I'd love to see a built-in reader mode that strips pages down to bare text, like in Firefox, Edge, Safari, and Vivaldi browsers.
As I'm getting older, it's getting harder to read small text. Also, in the mobile browser, sometimes pages have too many advertisements to read easily. Being able to just see the text at the right width and having the ability to scale up or down font sizes would be helpful. It would also be one less extension (and one less vulnerability) that I'd have in my browser. The ability to change colors (black text on white, white text on black, sepia tones) to reduce eye strain would also be a nice addition.